It is known in the art to utilize electro-mechanical actuators to select between two or more states of a device or system. For example, it is common to engage a brake with an electro-magnetic solenoid to stop and hold a motor shaft from turning. To engage the brake, the solenoid is electrically energized, causing a plunger of the solenoid to actuate and move a latching mechanism from a disengaged position to an engaged position such that the latching mechanism engages a face gear on the motor shaft. The solenoid is then de-energized. The brake is held in the engaged position until disengaged by any conventional means, such as energizing the motor.
Electro-magnetic solenoids suffer from a number of drawbacks. For example, the actuation characteristics of a solenoid depend upon, among other things, the properties of the electromagnet. In turn, the properties of the electromagnet are dependent on such variables as wire size, the number of turns of wire, plunger material properties, and air gaps in the solenoid assembly. At least some of these variables are difficult to control. As a result, solenoids must be built to exacting specifications, making them expensive and time-consuming to manufacture.
Another limitation of electromagnetic solenoids is that their shape is necessarily bulky owing to the volume required for the electromagnet, which typically has a central opening to slidably accommodate a plunger. The relative bulk of a typical solenoid limits its use where size is a constraint.
There is a need for an electro-mechanical actuator that can be manufactured easily and inexpensively. There is an additional need for an electro-mechanical actuator having a smaller package size than current electromagnetic solenoids.